Putting fixtures on a platform is never a good choice. It will always look second class. You don't say how much work you are willing to do yourself, but you can save much of the expense by buying a small rotary hammer and opening the floor yourself. Several companies sell a 3 function rotary hammer/drill for under $100 including chisels and several SDS drill bits, and this is quite adaquate for a DIY job like this. It's also very handy anytime you need to drill a hole in concrete. You will have concrete dust to clean up (UGH) but save long green in the process. Once the floor is open, the plumber can do his part.